Hi,
On 19/04/16 21:13, Gabriel Krisman Bertazi wrote:
> Under stress occasions some TI devices might not return early when
> reading the status register during the quirk invocation of xhci_irq made
> by usb_hcd_pci_remove. This means that instead of returning, we end up
> handling this interruption in the middle of a shutdown. Since
> xhci->event_ring has already been freed in xhci_mem_cleanup, we end up
> accessing freed memory, causing the Oops below.
>
> commit 8c24d6d7b09d ("usb: xhci: stop everything on the first call to
> xhci_stop") is the one that changed the instant in which we clean up the
> event queue when stopping a device. Before, we didn't call
> xhci_mem_cleanup at the first time xhci_stop is executed (for the shared
> HCD), instead, we only did it after the invocation for the primary HCD,
> much later at the removal path. The code flow for this oops looks like
> this:
>
> xhci_pci_remove()
> usb_remove_hcd(xhci->shared)
> xhci_stop(xhci->shared)
> xhci_halt()
> xhci_mem_cleanup(xhci); // Free the event_queue
> usb_hcd_pci_remove(primary)
> xhci_irq() // Access the event_queue if STS_EINT is set. Crash.
> xhci_stop()
> xhci_halt()
> // return early
>
> The fix modifies xhci_stop to only cleanup the xhci data when releasing
> the primary HCD. This way, we still have the event_queue configured
> when invoking xhci_irq. We still halt the device on the first call to
> xhci_stop, though.
>
> I could reproduce this issue several times on the mainline kernel by
> doing a bind-unbind stress test with a specific storage gadget attached.
> I also ran the same test over-night with my patch applied and didn't
> observe the issue anymore.
>
> [ 113.334124] Unable to handle kernel paging request for data at address
> 0x00000028
> [ 113.335514] Faulting instruction address: 0xd00000000d4f767c
> [ 113.336839] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 113.338214] SMP NR_CPUS=1024 NUMA PowerNV
>
> [c000000efe47ba90] c000000000720850 usb_hcd_irq+0x50/0x80
> [c000000efe47bac0] c00000000073d328 usb_hcd_pci_remove+0x68/0x1f0
> [c000000efe47bb00] d00000000daf0128 xhci_pci_remove+0x78/0xb0
> [xhci_pci]
> [c000000efe47bb30] c00000000055cf70 pci_device_remove+0x70/0x110
> [c000000efe47bb70] c00000000061c6bc __device_release_driver+0xbc/0x190
> [c000000efe47bba0] c00000000061c7d0 device_release_driver+0x40/0x70
> [c000000efe47bbd0] c000000000619510 unbind_store+0x120/0x150
> [c000000efe47bc20] c0000000006183c4 drv_attr_store+0x64/0xa0
> [c000000efe47bc60] c00000000039f1d0 sysfs_kf_write+0x80/0xb0
> [c000000efe47bca0] c00000000039e14c kernfs_fop_write+0x18c/0x1f0
> [c000000efe47bcf0] c0000000002e962c __vfs_write+0x6c/0x190
> [c000000efe47bd90] c0000000002eab40 vfs_write+0xc0/0x200
> [c000000efe47bde0] c0000000002ec85c SyS_write+0x6c/0x110
> [c000000efe47be30] c000000000009260 system_call+0x38/0x108
>
> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
> Cc: Roger Quadros <[email protected]>
> Cc: [email protected]
> ---
> drivers/usb/host/xhci.c | 27 +++++++++++++++------------
> 1 file changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 9e71c96..3272805 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -685,20 +685,23 @@ void xhci_stop(struct usb_hcd *hcd)
> u32 temp;
> struct xhci_hcd *xhci = hcd_to_xhci(hcd);
>
> - if (xhci->xhc_state & XHCI_STATE_HALTED)
> - return;
> -
> mutex_lock(&xhci->mutex);
> - spin_lock_irq(&xhci->lock);
> - xhci->xhc_state |= XHCI_STATE_HALTED;
> - xhci->cmd_ring_state = CMD_RING_STATE_STOPPED;
>
> - /* Make sure the xHC is halted for a USB3 roothub
> - * (xhci_stop() could be called as part of failed init).
> - */
> - xhci_halt(xhci);
> - xhci_reset(xhci);
> - spin_unlock_irq(&xhci->lock);
> + if (!(xhci->xhc_state & XHCI_STATE_HALTED)) {
> + spin_lock_irq(&xhci->lock);
> +
> + xhci->xhc_state |= XHCI_STATE_HALTED;
> + xhci->cmd_ring_state = CMD_RING_STATE_STOPPED;
> + xhci_halt(xhci);
> + xhci_reset(xhci);
> +
> + spin_unlock_irq(&xhci->lock);
> + }
> +
> + if (!usb_hcd_is_primary_hcd(hcd)) {
This implies that shared HCD must stop before primary HCD,
else we fall into the same situation again.
> + mutex_unlock(&xhci->mutex);
> + return;
> + }
>
> xhci_cleanup_msix(xhci);
>
>
You will have to send this patch to stable as well.
Reviewed-by: Roger Quadros <[email protected]>
--
cheers,
-roger
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